Wood frame construction recommendations for tile and stone floors

Building design guidelines and additional measures to accommodate sustained concentrated loads 

This article was derived from an article by Dr. Frank Woeste, P.E., Professor Emeritus at Virginia Tech and a wood construction consultant, and Peter Nielsen, cofounder of MGNT Products Group, LLC, a consulting and product design company for the tile and construction industries. This version of the information was generated by NTCA to provide a brief overview of their wood framing recommendations for hard surface flooring.


Two kinds of designers are involved in construction: design professionals responsible for performance and structural integrity and interior-focused designers responsible for the final appearance. Although they have very different roles, some of their decisions should be coordinated. For example, they should join forces when hard surface flooring – like tile and stone – is selected since these materials are on the heavier end of the spectrum, requiring more robust structures to support their weight. Hard surface floors are also more susceptible to problems than flexible floor types are when the weight of a concentrated load, like a dreamy kitchen island, is not adequately designed for. This article provides guidelines to design professionals for specifying adequately supportive structures for tile and stone floors in new construction wood frame buildings.

Designing for dead load

Sagging book shelves illustrate the concept of creep deflection; over time, shelves that are not strong enough for the weight they are loaded up with will bow.

A key factor is “dead load,” which is the cumulative weight of everything that a structure needs to support continually, including the flooring. When the actual dead load in a wood frame structure exceeds what was designed for, it over stresses the wood framing and over time can result in excessive “creep deflection,” a permanent bowing of the structure. An easy way to envision creep deflection is to picture an overloaded bookcase. The shelves will bow over time – and permanently – under the weight of the books.

Similarly, a home or building can be overloaded, for example by being structurally designed for luxury vinyl planks (LVP) flooring rather than the interior designer’s vision for ceramic planks. Some creep deflection is inherent and expected in wood frame construction, and not an issue for tile and stone floors. Overloading is what causes excessive creep deflection, possibly beyond what a tile or stone floor can withstand. Potential for and severity of a tile flooring issue because of excessive creep is tied to the amount of overloading and passage of time.

Weighty design features, like large kitchen islands with solid surface tops, and heavier-than-usual appliances, such as a Sub-Zero refrigerator, are examples of concentrated dead loads that additionally need to be designed for, structurally. This is true regardless of flooring type, but something to be especially aware of when the floor will be ceramic or stone tile. That’s because rigid, hard surface flooring materials are where concentrated overloading of a wood frame structure might become visually apparent, in the form of cracks, due to their inability to bend.

Baseline weights to factor into dead load 

To facilitate adequate structural design for tile and stone floors, the TCNA Handbook for Ceramic, Glass and Stone Tile Installation provides the approximate per square foot weight of tile, stone, and installation materials, individually by material type (i.e., 1/2” thick cement board weighs 4 lbs. per square foot) as well as cumulatively by installation method (i.e., Method F144 weighs 8 or 10 lbs. per square foot, depending on whether 1/4” or 1/2” cement board is used). Using this information, located in Appendix B, building designers can arrive at accurate dead loads. 

Appendix B of the TCNA Handbook is a compilation of material and system weights.

Method F141 Stone weighs 23 pounds/square foot with a 1-1/4” mortar bed.

Accurate dead load is important because dead load influences the maximum span (length) of wood joist that can be used, per International Residential Code (IRC) guidelines. These guidelines provide maximum allowable joist span separately for an assumed dead load of 10 psf and 20 psf. Remember though, dead load is not just the flooring. So, while the separate span tables may be generally used according to flooring type (e.g., follow guidelines for 10 psf dead load when lighter floorings like carpet will be installed, and guidelines for 20 psf dead load for tile and stone), one should not assume they apply in all situations. Additional dead load could be present from other elements, causing total dead load to exceed 10 psf where a lighter floor finish will be installed or exceeding 20 psf where ceramic or stone tile will be installed. Not to mention, some tile and stone installation methods on their own exceed 20 psf, which demonstrates that IRC span tables aren’t always enough.

Research indicates that an even more important consideration for tile and stone floors in wood frame construction is the thickness/stiffness of the subfloor, although not necessarily because of system-creep-inducing overload. Rather, the subfloor sheathing could simply deflect (bend) between joists under an applied load more than a hard surface tile can withstand, even if the sheathing is otherwise adequate within the full design scheme to support the expected loads. 

In Method F144, the wood subfloor can be 19/32” thick or 23/32” thick and relates to whether the installation methods falls under the residential or light commercial service rating.

This industry-specific consideration, not addressed in IRC, is addressed in the TCNA Handbook through more stringent deflection limits. Specifically, the TCNA Handbook limits deflection under concentrated loads, whereas IRC deflection limits are for uniform loads. What this means for building designers is that the minimum subfloor thickness/stiffness required by code for strength may not be enough. A thicker/stiffer subfloor may be needed to limit subfloor bending between joists. More robust framing may also be needed, again to go beyond the strength consideration to further limit bending related to concentrated loads. The heavier and more concentrated the load, the greater the need to beef up the floor framing to limit bending.

An example: the large kitchen island

As an example, consider the large kitchen island scenario. With 30mm (3cm) thick stone tops and normal contents being stored inside, this popular kitchen feature could present a 40 psf dead load, calculated by using the square footage of the island’s footprint as the area. In service, the framing and subflooring directly below and around the island is subjected to a substantial sustained load that produces creep deflection, but only in that area. As such, for hard surface floors, building design should incorporate more stringent framing requirements in areas where concentrated dead loads are expected, with kitchen islands a particular focus because of their widespread use. 

Because this kitchen island is oriented parallel with the wood joists, its weight is on fewer framing members.

It’s not practical, though, to expect a customized calculation and specification for every kitchen island. A more practical approach would be to follow general guidelines that are widely effective and easily incorporated into documents and processes. 

Since large kitchen islands are frequently paired with ceramic or stone flooring, it makes sense to have the following structural design parameters specifically attached to them: 

  • For solid-sawn and I-joists: joist spacing beneath kitchen islands shall be reduced by one-half and indicated on the joist framing plan.
  • For floor trusses: floor trusses beneath kitchen islands shall be doubled. 

Designing for hard surfaces checklist

These suggestions are in addition to the following recommendations, some of which were provided earlier in the article but are restated here in the interest of supplying a complete “designing for hard surfaces checklist”: 

  • Prepare construction documents that contain:

º the TCNA Handbook installation method

º the weight of the installation method (from TCNA Handbook Appendix B)

º the footprint of the kitchen island (and other heavy equipment)

º a specification that joists shall be doubled, or spacing reduced by half, beneath an island

  • Require floor system designs based on a “total load” that includes the actual weight of the installation method
  • Upgrade subfloor thickness (above what is given in the TCNA Handbook method being used) 
  • Require strongback bracing for floor trusses to minimize differential deflection of joists
  • Offer customers (homebuyers, owners) floor framing and subfloor “upgrades” for added protection against the likelihood of tile and grout cracks and annoying floor vibrations

The generalized “overbuilding” that some of these recommendations suggest may not seem an easy ask in an industry that prizes value engineering. But they do have enormous value – not in material cost savings – but from having effective boilerplate solutions to a common design challenge that are also practical with respect to implementation. Tile and stone professionals would be well served if these guidelines were better known and understood by building designers. TileLetter readers are encouraged to help make that happen by circulating and posting the information freely.

Planning for safety and style in commercial and residential showers

Curbless shower

Did you know January is National Bath Safety Month? While the origin of this month-long observation is unknown, the reason for it is clear: the bathroom is where most injuries happen within a dwelling, according to the National Kitchen and Bath Association (NKBA). And of course, people can get injured in any other bathroom they use; for example, in restrooms at work, in stores and malls, at venues for attending shows or events – the list goes on. Since so much of the tile industry’s work is done in some type of bathroom, TileLetter polled a group of NTCA members and technical staff on bathroom-safety-related observations and experience.

Consider DCOF

The BOT 3000 is a device for measuring the dynamic coefficient of friction (DCOF) of ceramic tile and many other hard surface floorings.

As you no doubt already guessed, all who were asked agreed that a main consideration is the dynamic coefficient of friction (DCOF) for any tile being used on a bathroom floor, because DCOF is essentially a measurement of a tile’s slip resistance. 

“We recommend tiles with the proper DCOF ratings and occasionally add an anti-slip treatment,” said Nyle Wadford of Neuse Tile in Youngsville, N.C., adding that his company will recommend a different selection if they think there may be a safety issue. Buck Collins, owner of Collins Tile in Ashburn, Va., concurred, saying, “We pay particular attention to this information and if we have any concerns they are discussed with the homeowner or GC before proceeding.” 

The ANSI A326.3 standard provides the test method for measuring DCOF of hard surface flooring materials and guidance on specifying hard surfaces relative to slip resistance. Tile Council’s technical bulletin on DCOF provides additional information in more reader-friendly language. Both publications and several other helpful DCOF resources are available for free download at https://www.tcnatile.com/industry-issues/dcof-acutest.html or https://bit.ly/2rYj861

Safety on the rails

The focus group was also asked about handrails and grab bars. Commercially focused tile companies are not likely to install grab bars, probably because other trades or the manufacturer will do that work, said NTCA Technical Trainer Robb Roderick. But residentially oriented companies seem to be installing them more and more, “especially in basement bathrooms that often serve as guest baths for clients with aging parents,” said Gianna Vallefuoco of Vallefuoco Contractors in Rockville Md. Collins agreed, saying his company puts them into about half the showers they build. Typically, he said, they install blocking (2” x 8” or 2” x 10”) between the wall studs where the grab bars will be installed after tiling, to ensure they can be firmly anchored. 

It’s becoming more common for blocking to be included at the framing stage, regardless of whether grab bars will be installed right away. “It’s easier to have these measures addressed as the bathroom is being created than after the fact,” said Vallefuoco. “We leave the client with a drawing of where they are located,” said Collins, “in the event they want to install them at a later date.”

Long gone are yesteryear’s grab bars. Safety accessories for the bathroom are now attractive and available in every style and finish, and price point.

Robert Showers, of Avalon Flooring in Cherry Hill, N.J., noted that some grab bars don’t require blocking nor drilling through tile. However, those option do have to be part of the original plan, as they are installed when the backer board is being installed. 

At the same time, a residential contractor may opt to avoid work related to handrails. Neuse Tile is often asked to put them in but rarely does, “because of the liability associated with a failure of the fastening methods,” said Wadford. “As a result of that and the variety of differing apparatuses that can be used, we leave that work to the expertise of others.”

Curbless showers: zero entry or barrier free?

A curbless shower facilitates easier shower entry and exit. This beauty was installed by Collins Tile.

Another growing trend is for showers to be curbless, also commonly referred to as zero entry. Curbless showers “go” with the minimalist style that we see across the industry, said Vallefuoco, while giving those with mobility issues easier entry into the shower. It’s important to note though, that a curbless shower is not necessarily “barrier-free,” a term often used to describe showers that comply with the Americans with Disabilities Act (ADA), which requires a lengthy list of additional requirements (for example, enough room for a wheelchair to turn around) in order for a shower or bathroom to be considered ADA compliant.

The group noted a litany of such additional details of bathroom and shower design and installation that could relate to safety: making sure shower floor tile is small enough to follow the three-dimensional conical shape of a floor that is sloped to a round drain, the angle of a curb when a curb is used, the height of a niche, shelf, or seat, etc.  

For instance, John Cox of Cox Tile in San Antonio, Texas, said that “We may position a seat or half wall to make sure there is some stability in the layout.” 

In addition, he points out the benefits of linear drains as a safety consideration. “Water flow maintenance can actually be better with linear drains,” he mentioned. “It depends on the grate (cover) and water flow. Some of them are more conducive to evacuating water. You have options on placement of locations for the drains. Front, back, to the sides are now viable options.”

And he pointed out that linear drains can pair better with popular larger-format tile. “With your traditional round drains, you have to use smaller tiles to make the slope to drain work,” he said. “You cannot use a larger-format tile due to the slope and not being able to bend the tile.”

NTCA Training Director Mark Heinlein added that in addition to these considerations being safety features, they represent opportunity for tile contractors and installers as “upsell” opportunities.

Good design encouraged from the planning stages

To develop effective slip/fall prevention recommendations for clients, insurance and risk management firm CNA studied the causes of slip/fall incidents. They found that, to reduce slip/fall incidents in bathrooms and showers, cleaning and maintenance practices often need to be improved to significantly reduce or eliminate soap residue from being left behind, because soap residue lowers a floor’s DCOF, meaning it makes a floor more slippery. Download the full report at tcnatile.com/images/pdfs/CNA_Risk_Control_Slip_and_Fall_Report_Final.pdf

Those who want to know more about bathroom safety, including potential business opportunity, might be interested in NKBA’s Certified Living in Place Professional (CLIPP) program, developed in partnership with the Living In Place Institute (https://nkba.org/clipp). The program is “devoted to accessibility, comfort and safety in every home” and addresses topics such as statistics and trends for the living in place market; medical, pharmaceutical and cognitive issues (for all ages); designs, products and installation; how to do a home safety assessment, and other business opportunities related to safety.

“There are lots of tiny details that often get overlooked in the planning stages,” said Vallefuoco. “No client wants to have to step or reach in awkward positions to access shower products.” Her sentiment mirrors the NKBA’s: “Part of the battle with convincing clients to consider the principles of living in place when starting a remodeling project is that no one wants to be thought of as ‘old’ or ‘incapable.’ Designers must tread a delicate line in explaining that ‘living in place’ is really just ‘good design’ that can accommodate anyone’s needs, now or in the future.”

CERSAIE 2018: Tiling Town attracts more than 1K visitors

TEC logoAt CERSAIE 2018, the seventh edition of Tiling Town event attracted more than 1,000 visitors (+15%), taking advantage of the new CERSAIE layout that brought together exhibitors of installation equipment and materials in halls 31 and 31A. These logistics facilitated meetings between visitors and tile installers and master tile layers from Assoposa – the Italian association dedicated to ceramic tile installation. Tiling Town offered daily showcases of installation work with large-size panels and slabs. 

There were three separate initiatives devoted to slab installation:

  • Promotion of Assoposa training courses for slab layers. Slab installation is a completely new kind of work that requires specialist skills. With this in mind, Assoposa has organized a specific training course designed to transform tile layers into professionals capable of installing large slabs in compliance with standards in all operating conditions. The four training modules presented at CERSAIE were held at the Scuola Edile (building school) in Reggio Emilia this year on November 29 and 30 and December 1. 2019 dates are:
  • ° January 10, 11, 12, 31 
  • ° February 1, and 2 
  • ° March 14, 15 and 16.
  • Participation is free and reserved for Assoposa members with the professional tile layer or master tile layer credentials. 
  • Seminars for architects and designers that qualify for professional training credits in Italy, organized to encourage design projects using these innovative products and to promote the use of large slabs. All problems relating to the new products can be resolved by qualified specialist retailers and installers.
  • A proposal for managing logistics and transport of these new products by drawing up a series of non-obligatory “Good Practices” for the logistics and transport of slabs in coordination with manufacturers, transporters and retailers. 
A new layout at Cersaie facilitated meetings between visitors and tile installers and master tile layers from Assoposa.

A new layout at Cersaie in halls 31 and 31A facilitated meetings between visitors and tile installers and master tile layers from Assoposa – the Italian association dedicated to ceramic tile installation.

Tiling Town 2018 also hosted installations devoted to special cutting and the “continuous vein” effect. Replicating the successful “RIGHT/WRONG” initiative of previous years, these showcases clearly demonstrated how a carefully designed installation project based on the tile’s vein pattern produces far superior results to a random layout. The exceptional aesthetic results achieved in the floor tile waterjet cutting demonstration further underscored the importance of proper installation.

Software for online compilation of the Traceability Sheet in accordance with Italian standard UNI 11493 was also presented. This sheet must be issued to the client by the contractor or sub-contractor and must provide an orderly and technically correct description of the key aspects of the operations performed, the materials used and the professionals involved. The Traceability Sheet serves as a kind of identikit of a ceramic tile installation, a document that sets out the key characteristics of a floor installation and validates the work of Assoposa member tile layers.

Eight new professional certification courses have been scheduled for the qualifications of tile layer and master tile layer and will be held in the period from October 2018 to March 2019 in the Italian cities of Bergamo, Cuneo, Padua, Reggio Emilia, Avellino, Pisa, Brindisi and Frosinone.

Tiling Town offered daily showcases of installation work with large-size panels and slabs.

Tiling Town offered daily showcases of installation work with large-size panels and slabs.

EITA (European Innovative Tile Academy), an advanced training school for instructors, was presented with the aim of promoting training courses for slab layers organized in accordance with a shared European standard at various national levels.

“What five years ago seemed like a dream – the creation of a highly respected association of professional ceramic tile layers and dealers with hundreds of members and a continuous, high-quality program of activities – has now become reality,” commented Paolo Colombo, Chairman of Assoposa.

There were three separate initiatives devoted to slab installation

There were three separate initiatives devoted to slab installation.

Cersaie 2018 and the activities of Tiling Town also saw a surge in applications for Assoposa membership (30% more than at Cersaie 2017). Following an intense promotional campaign, visitors showed a keen interest in the initiatives organized by Assoposa, including the presentation of a highly popular illustrated tile installation manual entitled “Assoposa per noi” which was distributed free of charge at the show. 

Apprentice competition tests hands-on prowess and book learning

From mud to mortar, BAC/IMI contest highlights benefits of training


TEC logoEvery three years, the top tile-layer apprentices in the International Union of Bricklayers and Allied Craftworkers (BAC) head to Bowie, Md., tools in tow, to compete for a top score in a rigorous test of hands-on skills and technical knowledge. Organized in conjunction with the International Masonry Training and Education Foundation (IMTEF), which provides training for BAC members and is funded through the International Masonry Institute (IMI), the triennial event celebrates the trowel trades and the trade workers committed to learning them through BAC’s apprenticeship program. 

A schematic showing what apprentices’ finished test modules should look like.

California’s David Perez earned the highest score, but, said IMTEF’s Lupe Ortiz, “They’re all winners.” He explained that the 13 apprentices – who spent a day being closely scrutinized by top BAC/IMI tile instructors and craftworkers from various parts of the country – had won the similar competitions held at the local and regional levels to advance to this final round. Ortiz was one of the contest judges, a role befitting someone who has trained scores of apprentices in California and is known by many in the industry as a stickler for strict adherence to installation standards and quality. He is now a regional director of apprenticeship and training for IMTEF.

The hands-on component of the competition included a demandingly broad scope of skills tests, all of which had to be done within a strictly enforced time limit. Mudding walls – arguably one of the most difficult and increasingly lesser-known processes related to installing tile – was reintroduced into the competition program this year, noted Gavin Collier, an apprentice coordinator and contest judge. (He also played helper for the day, loading apprentices’ mortar stands with wall mud and cleaning buckets and tools.)  

An apprentice in the final stages of the mortar bed wall portion of the hands-on test.

Including wall mud in the curriculum helps keep the ability to produce mortar bed walls from becoming a lost art. An ever-expanding array of backer boards and thinsets has gradually replaced much of the mortar bed work performed by tile setters, especially on walls due to fewer reasons mortar bed walls might be needed. Instead, custom-sized and shaped showers and multi-drain areas like commercial kitchens have kept mortar bed work on floors more necessary. Accordingly, mortar bed work is more widely practiced by residential and commercial installers alike.  

To prove their wall mud prowess, the contenders had to produce flat, plumb-faced walls with plumb and level perimeter edges, sized to the correct height and width for the tile installed over it. They also had to stay within industry standards for minimum and maximum thickness. In addition to the two adjacent walls being closely inspected for these considerations, evaluators checked the corner where they intersected for squareness. 

A view of the apprentice contestants working on their modules.

After putting up their wall muds, the apprentice contestants screeded and floated a mortar bed floor, installed tile with a challenging layout and trim pieces, and finished their test modules with grout and caulk. According to Ortiz and Collier, a total of about 40 installation details were carefully inspected and scored by the four journeyman evaluators, who quite obviously took their role seriously. Over the course of the day they compared notes constantly, and quietly but passionately debated their observations to arrive at their final evaluation scores. The individual aspects of the test module that they scored were the critical requirements and workmanship standards aimed at avoiding installation failures and aesthetic issues. Combing the mortar correctly to achieve proper mortar coverage is imperative, said Ortiz. “In our trade you have to pay attention to the small details,” he added.

Evaluators confer and judge the work of the apprentice contestants.

The following day the apprentices took a closed-book written test focused on tile industry ANSI standards and the TCNA Handbook of Ceramic, Glass and Stone Tile Installation. Combined scores were tallied, and Perez was announced champion for the tile division of the contest. 

Ortiz and Collier have been providing structured education and skills training to tile setter apprentices for several decades and are deeply committed to continued program developments and improvement. At the same time, they acknowledge that the top-performing apprentices’ high skill level is not only a result of the foundational skills built in those classrooms. The contractors they work for and installers they work under day-to-day are a significant influence on apprentices’ development, they said. 

“What they expect and how they have them do things in the field has to support what IMI trainers are showing them,” said Collier. Apprentices are on the job so much more than they are under an instructor’s tutelage, he added. When it comes to Perez and the other 12 apprentices who competed, it’s clear that this is happening.

California’s David Perez was the champion for the tile division of the contest.

StonePeak Ceramics celebrates expansion

StonePeak Ceramics celebrates $70 million expansion to Crossville, Tenn. plant

New Continua production line aims to produce 1,000 5´ x 10´ gauged porcelain panels a day


Crossville, Tenn. – On September 12, a group of customers, press, state and local dignitaries, and company management assembled at the StonePeak Ceramics plant here to celebrate the expansion of the first U.S.-based plant to produce 5’ x 10’ gauged porcelain panels.

The $70 million expansion adds 160 workers to the facility, which now measures 1 million square feet. Federica Minozzi, CEO of the Iris Ceramica Group, parent company of StonePeak, SapienStone, FMG, Ariostea, Eiffelgres and Fiandre USA, spoke during the ribbon-cutting ceremony, stating that not only is this plant the first in the U.S. to produce gauged porcelain 5’ x 10’ panels, but it’s the first in the world to also offer the capacity to cut those panels to smaller sizes such as 12” x 12”. Panel thicknesses range from 6mm to 2cm.

“We didn’t even do this investment in Italy,” she said. “We decided to do it in Crossville.” 

Clays are sourced from the Carolinas, Kentucky and Tennessee to manufacture the panels, said Fiandre USA’s director of sales and marketing Eugenio Megna, who led visitors on a tour through the plant. 

Iris Ceramics Group CEO Federica Minozzi with StonePeak leadership and state and local dignitaries, cut the ribbon on the Crossville Tennessee’s factory expansion. It is the first in the world that produces 60˝ x 120˝ gauged porcelain tile panels and also cut sizes down to 12˝ x 12˝. This $70 million expansion also adds 160 workers and at peak will produce 1,000 panels a day.

Fiandre USA’s Eugenio Megna led tours through the new plant expansion. This A-frame filled with porcelain panels is ready for shipping, and holds 25 5´ x 10´ panels on each side.

The company uses the Continua production process and Sacmi machinery on the line, and utilizes sophisticated inkjet graphics to achieve looks like Calacatta or other aesthetics that are nearly indistinguishable from natural stone, as well as other in-demand looks. Random patterns, continuous veining and bookmatching can also be achieved here. It takes two hours from start to finish to produce a porcelain slab, and the end product is 25-30% harder than granite, when measured on the Mohs scale. Full size panels including StonePeak’s Plane 2.0 line, are shipped on A-frames, 25 to a side. The line has been operational since May.

Dignitaries praising the investment in the Crossville, Tenn., local economy included Angela Regitko, business development consultant for the State of Tennessee, Crossville Mayor James Mayberry, and newly elected County Mayor Alan Foster. Foster noted that StonePeak has made a $200 million investment in machinery and its facility since it opened in 2005, and has provided jobs for 400 workers in Crossville. 

Distributors weigh in on GPTP U.S. production

At the post-tour party on the rooftop bar of the Thompson Nashville are (l to r) StonePeak Ceramic’s Todd Ware, exec vp of national accounts;Leonardo Pesce, vp of operations; and Iris’s Marco Portiglia, sales & marketing director.

“StonePeak is taking a step ahead of their competitors by being the first to produce the large panels in the U.S.,” said Bill Spina, president of Standard Tile Supply Co., Totowa, N.J. “I feel it is a natural to be used as counter tops. In our area, it is becoming more accepted for commercial projects and it should substantially help in residential applications now that they can cut to smaller sizes.”

Tom Cosky, Nautilus & Aquatica Program manager for IWT, called StonePeak’s new domestic product with the Continua line a “game changer as far as pricing of large unit panels. They are passing along significant cost savings making it a much more competitive product.”

Mediterranea’s Michael (l) and Don Mariutto at the StonePeak afterparty atop the Thompson Nashville.

Cosky sees installation as a continuing hurdle. “The larger challenge still remains with the training of qualified installers, but that’s another thing StonePeak seems very aggressively tackling on their own,” he said. “My end of the equation – distribution – requires a different set of logistical issues than the traditional tile distributor must face to get in the game. We are encountering more and more inquiries for these panels and we see a real future for it as long as we can adapt to handle the opportunity.”

“StonePeak’s new gauged porcelain tile equipment at their Tennessee manufacturing plant will be a game changer for the U.S. tile industry,” said Brian Atkinson, president of The Masonry Center, Inc., in Boise, Idaho. “Production of StonePeak’s large-sized porcelain tile is now closer to their wholesalers, which will shorten transportation time and help us to better serve our customers.”
After expressing thanks to employees and state and local support, Minozzi revealed that the decision to hold the ceremony on September 12, a day after the 17th anniversary of the September 11 attacks in the U.S., was intentional, as a way to both honor the significance of the day and to celebrate the resilient, renaissance spirit of the USA to rebuild after that tragedy. “I love America,” she said. 

In the evening, guests and hosts gathered for a soiree at LA Jackson, the rooftop bar of the new Thompson Nashville.

Mock-ups eliminate miscommunication and reduce install failure risk

Mock-ups are great tools for managing customers’ expectations, which in turn can reduce risk and lead to successful installation. Today, we’ll define what a mock-up is, and explain the many advantages of using them. 

Mock-up module.

A mock-up can be either a partial or full-size structural model using exact construction materials, specifications and techniques. They allow all those involved to evaluate an actual three-dimensional representation of a project. They also allow us to experience at full scale what could only be hinted at with drawings or small architectural models. Mock-ups allow us to access the functionality, aesthetic and quality of the actual products down to the smallest details. If the old saying “A picture is worth a thousand words” is true, a mock-up must be worth a considerable amount more. 

Oftentimes, mock-ups are required in commercial projects. It may seem that the additional expense associated with doing a mock-up is unnecessary but, in the end, it allows the team to foresee problems and solve them before they develop on a larger scale.

Jobsite conditions, shade variation and grout joints

Mock-ups get you involved early and allow you to access jobsite conditions such as: does the site have power, water, correct temperature, and lighting? It gives us the opportunity to establish the needs for a successful installation. With tiles transitioning to larger and larger sizes, mock-ups help installers set a standard for how flat surfaces must be to install tile. If we run into a problem with poorly-done concrete or framing, we can explain our needs for flat surfaces before they pour the next series of slabs, or frame the next group of rooms. 

Mock-ups help installers set a standard for how flat surfaces must be to install tile.

It seems we are continually pushed by faster and more demanding schedules to complete projects. Timing the installation of a mock-up can be extremely beneficial in determining the amount of total time a project will take, as well as the amount of manpower necessary to reach a desired deadline.

Many of us have probably had issues with showroom samples not actually matching the delivered material, especially with stone. Sometimes, a stone sample could have been quarried months or possibly years before the actual stone is selected and ordered. A mock-up shows you the actual current material appearance. Also, when some tiles have highly varied shading, it’s difficult to appreciate the overall look apart from an on-site mock-up with the actual material. Our industry has Aesthetic Classifications for shade variations that range from V0 to V4. The V0 are the most uniform in shade, while the V3 and V4 are the most varied. When using the more highly varied tiles it takes a larger area of tile to truly appreciate the overall appearance.

Shade variation courtesy of Architectural Ceramics.

The last few years, the trend has been for smaller and smaller grout joints. It seems everyone loves tile but hates grout. Mock-ups can set an agreed-upon grout joint size. Our industry addresses minimum grout joint size. It states that we should never have a grout joint less than 1/16˝. It also explains that a grout joint should not be any smaller than three times the facial variation of the tile itself. Normally with a calibrated tile that would be around 3/16˝, and with rectified tile it would be 1/8˝. Most of our customers have difficulty visualizing what a 3/16˝ grout joint looks like. A mock-up eliminates that problem and allows the customer to better communicate their desires.

Outsmarting lippage before it happens

Plank and other rectangular shape tiles have grown dramatically in popularity. When tiles are manufactured, they are fired in a kiln. This process can warp the tile or make them bow. When plank or rectangular shape tile are set in an offset or brick pattern, the warpage in those tiles can create lippage in an installation. Lippage is basically when two tiles don’t meet on the same plane. Our industry has addressed this situation and says we should have no more than a 33% offset with tiles over 18˝ in length. It goes on to say if a stagger of more than 33% is called for, a mock-up should be done and approved.

One of the many benefits of being a member of the NTCA is technical support. One of the most prevalent calls we receive is about wash wall lighting. The design community has embraced this lighting that is located in the ceiling close to the wall and casts light down the wall and creates an undesirable shadowing effect. The lighting reveals inconsistencies in the wall, tile, and the work. In a large commercial project where this type of lighting is used, a mock-up can be a great asset. Finding out early the effects that light will have on the installation can save a lot of headaches and money. Moving the lights out from the wall can make a huge difference. Discovering this information early from a mock-up makes the process quicker, easier, and cheaper.

Setting expectations with your mock-ups

One thing to consider when doing your mock-up is to be mindful of who you are selecting for that installation and to create the mock-up. If you have a large crew with several installers, there is a tendency to pick your best people to do your mock-up. Remember, this is an example of what the owner will expect throughout the project. Inevitably, we have different employees that work at different speeds with different skill sets. It would be best to pick someone of average skill and speed for your group. This will give a more realistic expectation of what you can deliver. It’s said that it’s better to undersell and over deliver, than oversell and under deliver.

Once the mock-up is complete, communicate potential problems, and get a formal acceptance of the installation for the standard on the remainder of the project.

In conclusion, I hope you understand how mock-ups can:

Allow you to evaluate environmental conditions on the jobsite

  • Access substrate flatness
  • Define roles and responsibilities of each trade
  • Give a good indication of the time it will take to complete a project
  • Allow for evaluation of actual tile and grout color and shading
  • Set an agreed upon tile pattern and grout joint size
  • Help eliminate issues with critical lighting
  • Manage customers’ expectations and reduce risk.

Ideal underlayment and tile setting strategies


Every month, NTCA offers free online webinars on a range of topics. Industry experts share their wisdom during these one-hour events that can be watched on a computer, phone, tablet or in a conference room with staff and crew. If you miss a webinar, NTCA archives them for watching at your convenience. Visit www.tile-assn.com and click the Education & Certification tab for news on upcoming talks and archived presentations. 

This month, we revisit the March 20, 2018 webinar entitled “Ideal Underlayments and Tile Setting Strategies,” presented by Tom Plaskota, technical support manager for TEC/H.B. Fuller Construction Products – and provide an overview. For the complete webinar, follow the directions above. 

Plaskota addressed several main topics in his talk. For this article, we will focus on the first two topics: 

  • What are self-leveling underlayments and how do they work?
  • Benefits of self leveling underlayments.

What are self-leveling underlayments and how do they work?

ASTM F2873 provides a definition of self-leveling underlayments (SLUs) that hinges on four key concepts:

  • They are poured and flowable mortars
  • They are composed primarily of hydraulic cements such as Portland cement materials and calcium aluminate. These compounds continue to harden under water.
  • They may require a primer to enhance bond strength and reduce development of pin holes.
  • They are designed and intended to provide a flat, smooth surface for the finished floor covering – ceramic tile or natural stone. 

Self-leveling underlayments achieve their high-flow properties through the use of flow agents that produce a pancake-batter-like consistency. They are also formulated to be non-shrinking and non-cracking. Unlike a thin-set mortar, SLUs are commonly set in thicknesses of up to 1/2” to 2”and are formulated to not shrink or crack at that thickness. Components like calcium aluminate allow the SLU to cure quickly, so that in many cases, the underlayment will support foot traffic and allow for tile setting in a matter of hours. 

Benefits of self-leveling underlayments

Plaskota approached the subject of SLU benefits by addressing common questions and objections about self-levelers – and the reality of the benefits they bring.

Self levelers aren’t necessary for tile installations

Reality: You need self-levelers for successful tile installations to ensure that the substrate is flat. They help expedite tile installations and save installers from having to make subfloor adjustments, while improving subfloor quality that reduces lippage and cracked or damaged tile. In addition, SLUs help you more easily and quickly achieve the tighter flatness requirements for today’s popular large-format tile, with in-demand tight grout joints: 1/4” in 10’ and 1/16” in 12” for tiles with all edges shorter than 15” and 1/8” in 10’ and 1/16” in 24’ for tiles with at least one edge measuring 15”. Gauged porcelain tile panels that measure as large as 3’ x 10’ or even 5’ x 10’ are not forgiving when it comes to subfloor flatness and so require the use of SLUs. 

I only need SLU for resilient/sheet vinyl – imperfections in substrate aren’t as ‘visible’ with tile.

Reality: The use of bonding mortar to level, flatten or fill substrates does not conform to tile industry standards. Some tile setters mistakenly believe they can “fill” substrates with thin-set or “medium-bed” (now known as large-and-heavy-tile-mortar) mortar. But these products were not made for leveling substrate. Instead, they are designed to accommodate the features of the tile, such as preventing a large, heavy tile from slumping into the mortar. They also address allowable warpage, which is greater in a larger tile, so there’s a need for a bit thicker mortar under the tile to accommodate the irregularity in the tile. Even setting small tiles on an uneven substrate can result in hazardous and unsightly lippage and callbacks. 

Self-leveling runs up extra charges. 

Reality: NOT installing a self leveling underlayment may result in costly call backs. You are going to have to smooth or level your floors. SLU is a great, efficient way of doing that to reduce callbacks. 

Self-levelers are time-consuming to apply; slows down the whole project schedule 

Reality: Efficiencies in installation methods and fast-setting underlayments allow for same-day tile installations. These are not your grandfather’s SLUs – they’ve come a long way and feature enhancements, and advanced technology primers that may eliminate the need for shot blasting over clean concrete, regardless of porosity. They may even go over some types of coatings such as curing compounds, high-performance topical coating like epoxies or cutback residue. In this case, the primer/SLU combo is a great time and money saver. Be sure to consult the SLU manufacturer and confirm the application. In addition, tools and equipment such as rakes, buckets or bucket carts that can be managed by one person can help expedite SLU application. 

Again for details of this talk, click the webinar link under the Education & Certification tab on tile-assn.com. This link also announces upcoming webinars and houses the archives of talks from the last few years.

Tech Talk – May 2018 – TEC® Products help set a perfect stage for the new Global Learning Center at Walsh University

TEC® Products help set a  perfect stage for the new Global Learning Center at Walsh University

The new Global Learning Center at Walsh University in North Canton, Oh., will truly be a communications hub for students and faculty. The two-story atrium building has an open, modern design to encourage and support maximum interaction. The sunlight-filled facility will house student labs for fast-growing technology-based fields of study such as computer engineering or video production, The Forum – an aptly named space for two of Walsh’s important research institutes – contains an atrium café, meeting areas and more.

The building’s open design incorporates the use of many windows, curved glass railings and round support columns. Stylish large-format tile flooring adds to the modern feel with 30” x 30” and 15” x 30” thin gray tiles covering about 11,000 sq. ft. on both the first and second levels. For an additional 1,000 sq. ft. of tile in the restrooms, sleek 12” x 24” thin panels were selected. 

Distributor Virginia Tile of Cleveland helped ensure that TEC® flooring installation products were specified to meet the unique challenges of the job. With a tight construction timetable and lots of curved columns and curved flooring lines along atrium railings, installation of the Global Learning Center’s large tile panels required special skills. Luckily, Youngstown Tile and Terrazzo (YTT), a NTCA Five Star Contractor, had the skills needed to accomplish this challenging tile installation.

Substrate challenges

When YTT arrived at the Global Learning Center site, they quickly discovered that leveling the substrate would be tough. The new concrete had varying elevations. On the first floor, there were frequent dips and swirls up to 1/2”. On the second level, the concrete changed depth by up to 1-1/2” across a 6’ section. In addition, the many columns and curves added leveling complexity. 

After priming with TEC® Multipurpose Primer, YTT pumped new TEC® Level Set® 300 Self-Leveling Underlayment to correct the variations. Josh Cohol, President of YTT, explained, “The new TEC Level Set 300 created as close to a perfectly flat surface as I’ve seen. We pumped the product and noticed its excellent flow ability to reach around the many columns and follow the curved flooring edges. Even applied at a depth of 2”, it was walkable in just a couple of hours.” Cohol appreciated frequent on-site support from H.B. Fuller Construction Products’ Charlie Renner, Technical Sales Manager, and Ron Sheldon, Technical Services Manager.

To mitigate concerns about cracks migrating up through the large, thin tiles, TEC® HydraFlex™ Waterproofing Crack Isolation Membrane was specified. YTT rolled on the membrane before troweling on the mortar. For the larger expanses, TEC® 3N1 Performance Mortar was used. TEC 3N1 is a lightweight premium mortar with Easy Trowel Technology™ for superior handling and extended open time – appreciated for large spaces and large tiles. 

The Global Learning Center’s round columns required challenging radius tile cuts and a 17° angled layout to follow the column line on the second floor. YTT’s experienced installers successfully navigated through all the challenges with impressive results. For the bathrooms, TEC® Ultimate Large Tile Mortar was used to handle the large tiles on both the floors and walls, where its non-slip and non-slump properties made tiling much easier. 

To finish the dramatic tile installation, YTT grouted with TEC® In-Color™ Advanced Performance Tile Grout. YTT was impressed with how easy it was to grout with the ready-to-use product. TEC In-Color Grout is crack-resistant, stain-proof, and chemical-resistant with no sealing required. In other words, the product was just right for the very large tiles set in the high-traffic spaces of Walsh University’s new Global Learning Center. 

Upon completion of the project, YTT’s Josh Cohol did a walk-around with Charlie Renner, who summed up the quality of the work when he said, “This installation had a lot of challenges, but the tile looks flawless.” 

For more information about the products used at Walsh University, visit www.tecspecialty.com.

©2018 H.B. Fuller Construction Products Inc. 

The 12” x 24” tile on the bathroom floor and walls was installed with TEC® Ultimate Large Tile Mortar.

Tech Talk – April 2018

Thin gauged porcelain tile – North American research, collaboration, and standardization

By Bill Griese, Director of Standards Development, Tile Council of North America and Noah Chitty, Director of Technical Services, Crossville Inc.

In February, TCNA’s Bill Griese and Crossville’s Noah Chitty traveled to Castellón, Spain, to lecture to the Congress of Qualicer 2018 on research and standardization of thin gauged porcelain tiles and tile panels (GPTP) in North America. Following are highlights of their white paper on this subject, which was presented at Qualicer 2018. The paper, in its entirety with works cited, is available online at tileletter.com.

ANSI A 137.3 and ANSI A108.19

 

In 2017, the North American tile industry released two new standards: ANSI A137.3, American National Standard Specifications for Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs, and its companion, ANSI A108.19, Interior Installation of Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs by the Thin-Bed Method bonded with Modified Dry-Set Cement Mortar or Improved Modified Dry-Set Cement Mortar. These standards, developed for the benefit of all tile consumers, are the result of a multi-year research and consensus process of the ANSI Accredited A108 Standards Committee, which includes participants from all industry sectors. 

These efforts aimed to establish a framework for specifications of products that are intentionally “gauged” to a specific thickness. Currently two classes of gauged tile products are defined by the standards: 

Those for wall applications from 3.5mm to 4.9mm and 

Those for floor and wall applications, from 5.0mm to 6.5mm. 

Other products, which either fall outside of these ranges or for which the manufacturer has not specifically provided a gauged-thickness designation, continue to be standardized under traditional tile specifications.

Terminology and strength criteria

One of the earliest topics on which the North American industry debated was terminology. These products were called “thin” tile, but since the same technologies are also used to create thick tiles – and end-users had increasingly prioritized tile thickness as a key characteristic – a new moniker was needed. Hence, the term “gauged” was born, basing the term on one used for other construction products – such as electrical wire and sheet metal – which carry different load capabilities and usage parameters across a variety of gauges. The group agreed to further differentiate gauged products based on their size, with gauged tiles being less than a square meter and gauged tile panels/slabs being greater than or equal to one square meter. 

In developing product performance criteria, the first key concern was breaking strength, as the North American requirement for traditional tiles was 250 lbf. Initially, very few – if any – thin gauged products met the requirement. Therefore, installed strength became the key to achieving performance levels comparable to those of traditional tiles whose exceedingly high breaking strength could often make up for flaws in mortar coverage or quality. With thin gauged tiles, though, the group chose to scrutinize how lower breaking strength may be offset by installation rigidity and increased mortar coverage.

Key provisions of the installation standard

To develop ANSI A108.19 Interior Installation of Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs by the Thin-Bed Method bonded with Modified Dry-Set Cement Mortar or Improved Modified Dry-Set Cement Mortar, a group of installers, architects, and manufacturers conducted countless experiments to discover application and embedding techniques that make possible maximum mortar coverage, particularly for tile panels/slabs. Through these experiments, standard setting procedures for gauged porcelain tiles and tile panels/slabs were developed that facilitate optimal workmanship and system integrity. 

Mortar application: It was determined that applying a layer of mortar to both the back of the panel/slab and the substrate would result in the necessary bond coat thickness of 3/16” (4.8mm) and would allow for full encapsulation of lippage control systems. Anything less than this method would result in an embedded mortar layer thickness that was insufficient to achieve the agreed-upon substrate tolerance of a maximum deviation of 1/8” in 10 horizontal feet (3mm in 3m) from the required plane when measured from the high points in the surface for floors.

Mortar properties: Mortar properties such as extended open time, flow to achieve coverage, and curing parameters appropriate to the application, as well as a requirement for suitable mortar identification through consultation with the tile and setting material manufacturer are specified in the standard. 

Trowels: Only Euro-trowel, Flow-Ridge trowel, and Superior notch trowel can facilitate ridge collapse without the need to press and slide the tile. The group agreed to standardize the use of such trowels.

Embedding procedures: For floors, physically walking on the surface in the following pattern produces the greatest supporting mortar coverage: 

1) walk down the centerline of the tile; 

2) take small shuffling steps left and right from center to push air toward the edges.

This standardized procedure is listed in ANSI A108.19 for embedding tile panels/slabs on floors. For walls, a vibration tool and weighted beat-in paddle are specified in order to achieve optimal coverage.

For walls and floors, a vibrational tool used at the perimeter, achieved full coverage on the edge, critical for overall durability in flooring applications, and also facilitated full encapsulation of lippage control systems. For these reasons, edge coverage achieved through vibration is a provision of ANSI A108.19. The standard minimum required coverage is 80% for walls and 85% for floors. Additionally, maximum void size was established as 2 square inches (1290 square mm).

Coverage calculation: A standardized evaluation to calculate coverage was developed. ANSI A108.19 states, “In any single square foot under the embedded tile, coverage… is calculated by measuring the voids and the marked off square foot and dividing by 144 square inches (929 square cm) where the dry set mortar is not in full contact from the back of the tile to the substrate.”

Substrates: Standardized suitable substrates for the installation of gauged porcelain tiles and tile panels/slabs are mostly consistent with those of traditional tile, with the exception of direct bonding to plywood floors, which requires the use of a mortar bed or specified backer board and referencing floor rigidity requirements established by building codes and other widespread industry specifications. 

Applicable to all substrates, ANSI A108.19 details required flatness as maximum deviation of 1/8” over 10’ (3mm in 3m) from the required plane when measured from the high points in the surface.

Material handling: Qualified labor and other provisions also taken into account through discussion and A108.19 standardization were adequate jobsite storage, space to maneuver panels, prevention of damage while handling and time for mortar curing. Another critical aspect of ANSI A108.19 involves usage of properly qualified installers who are equipped with proper tools and have acquired sufficient product knowledge and installation experience. 

There are several other key provisions contained within ANSI A108.19, including grouting, workmanship, movement accommodation, and maintenance, completing a very comprehensive specification for how to install products defined by ANSI A137.3. 

See link here for the full paper, including footnotes. 

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Tech Talk – Coverings 2018

Avoiding latex leaching from
tile setting materials

By Colin Cass, Techtile Consulting Pty. Ltd, Australia


This paper was recently presented at the Qualicer ’18 conference in Spain.

Abstract

The use of polymer/latex type additives that improve the performance of thin-set adhesives and mortars has been in common and increasing use since the 1960s. For decades there have been occasional references to some of these polymer/latex additives leaching from tile work to cause problematic stains on the finished surface. 

As a consultant looking at problems with tile-work over the decades, I have noticed an increase in this specific staining, called “latex leaching” that is sometimes confused with “efflorescence” staining. This staining is far more difficult to treat than efflorescence, but it is easier to avoid. Investigations into this staining have revealed certain changes in products and procedures that are associated with this increase.

This paper does not analyze the chemical aspects of the cause of this staining; rather it explains actions that can be taken by designers, specifiers, builders and tile installers to avoid this problem. 

Changes that make latex leaching more common 

In 1986, a Field Report of the Ceramic Tile Institute of America (86-5-1) titled “Installing Ceramic Veneers with Latex Modified Mortar & Grouts” used the term “Latex Leaching.” In May 1989, Tile & Decorative Surfaces expanded on the issue, opining that “rain is one of the biggest contributors to the leaching
problem.” 

The problem was raised again by the Tile Council of North America (TCNA), which reported the issue in the following way, but just related it to excess water mixed with the grout, not the thin-set adhesive. It stated: 

“What is latex leaching and dirt deposition? Less common than efflorescence is the white residue that can form on polymer-modified grout if the grout is subjected to excessive moisture before the polymers coalesce. Polymer additives are often added to grout to provide superior properties, commonly improved chemical resistance, reduced porosity, improved flexibility, and freeze/thaw stability. These additives are either already in the grout as re-dispersible powders or are added in liquid form. In both cases, grout mixed with too much water or cleaned too soon, or cleaned with excess water, can cause the polymer to migrate to the surface. In many cases (but not all), these polymers are white in color. When the excess water evaporates, the white polymer is exposed.”

While some minor whitish deposits are likely to come from excess water in the grout mix, the serious disfigurement that keeps returning and which is identifiable by having a clear, sticky component that has a characteristic acrylic odor, is from water under the tile, that carries uncured additive to the grout joints. See photos 1, 2 and 3. 

While the problem of latex leaching has been known about for decades, its increasing incidence can be attributed to several changes that have crept into the tile and construction industries over the decades. These changes are:

  1. Larger, denser tiles
  2. Increased use of latex/polymer additives
  3. Thicker adhesive layers 
  4. Increased use of screed isolation layers (membranes and uncoupling mats)

Larger, denser tiles

There has been a world-wide uptake of large-format tiles. 35” x 35” and 48” x 24” porcelain tiles are now commonplace, and the use of “thin tiles” such as Laminam and Kerlite are increasing. These tiles generally have less than 0.5% water absorption, and so water in the adhesive is not taken into the tile back as occurs with twice-fired tiles.

These large tiles are usually laid with narrow joints, usually between 1/16” to 1/8.” This means that moisture in the adhesive is very slow to move to the evaporation point at the joints. This results in slower drying times and slower curing times for the adhesive. 

Increased use of latex/polymer additives

More latex and polymer additives are being used because they are necessary for adequate bond strengths to be attained when dense tiles are used. On top of this, the range of adhesive additives has been changing to include water entrainers and retarders, which can slow the cure of the adhesive. 

Thicker adhesive layers

While “thin tiles” (aka gauged thin porcelain tiles or slabs) are installed using smaller notched trowels, it is general for tiles greater than about 24” x 12” to be laid using 1/2” notched trowels, with adhesive manufacturers usually calling for a minimum 1/8” depth of adhesive and 100% contact coverage. Most manufacturers of adhesives also call for large tiles to be “back-buttered” with adhesive, and this adds to the depth of adhesive coverage.

Some contribution to thicker adhesive layers also comes from unskilled tile installations and other construction trades’ workforce. If surfaces are not true and straight, then extra adhesive is required to pack the finished work out to its proper alignment. Preparation trades who fail to provide good surfaces – or tilers who have poor mortar screeding skills – end up using thicker adhesive layers.

Increased use of screed isolation layers/ membranes and uncoupling mats

For a number of reasons, including efforts to prevent efflorescence staining, there has been an increase in the application of waterproofing membranes over the top of mortar screeds. Often the aim is to prevent water entering the mortar screed and leaching calcium stains out. Such a waterproof membrane prevents moisture in the tile adhesive from being absorbed into the screed, thereby delaying curing and drying of the adhesive. 

The increased use of other dense layers over the screed, such as uncoupling, or crack-isolation membranes made of bitumen or plastics such as polyethylene, have a similar effect of preventing the absorption of water in the tile adhesive into the screed. 

Delayed curing and drying of latex/polymer modified adhesives

All of the above changes result in slower curing and drying of the tile adhesive. For internal tiling, this is not a great issue. It means wall installations need to have supports left in place longer to reduce creep, until a proper cure has occurred, and floors should not be trafficked for a number of days, instead of the usual 24 hours. But when it comes to external tiling, this slow curing and drying can be a major problem.

This delay in curing is specifically referred to in the TCNA Handbook, which at least since 2011 has stated under the heading Latex/polymer modified Portland Cement Mortar: 

“When installing 8” x 8” or larger impervious tiles over a waterproof or crack isolation membrane, or other impervious substrate, longer curing times will be required. A rapid setting latex/polymer modified cement mortar may need to be specified for faster curing. Because latexes vary considerably, the directions of the latex/polymer mortar manufacturer must be followed explicitly.”

Despite this call for the manufacturer’s directions to be followed explicitly, a review of a large number of adhesive product data sheets revealed no mention of delayed curing when dense tiles and the adhesive were used over impervious substrates.

The most ominous warning also comes from the TCNA Handbook, which states:

“When latex/polymer modified Portland cement mortar is used to install ceramic, glass, and natural stone tiles in an area that may not thoroughly dry out in use (e.g. swimming pools and gang showers, etc.) or where initial drying is inhibited (between tile and impervious substrates), it is recommended that the completed installation be allowed to dry out thoroughly before exposure to water. This drying period can range from 14 to more than 60 days depending upon the temperature and humidity and other climatic conditions.”

The issues caused by this delay in curing and drying emphasize the need to specify and use rapid-setting adhesives for all tiling where a delay in curing is likely to cause problems.

The cause of latex leaching 

The problem of latex leaching is not widespread on external tiling. This proves that the adhesives, mortars and installation systems used are suitable and meet the needs of the industry. However, under certain conditions, some components of the latex/polymer modified adhesive leach out and cause staining.

Investigations at more than a dozen sites with latex leaching in Australia revealed a common cause. All the instances occurred when rain fell on uncovered and ungrouted tiling. In one apartment complex, rainfall charts and construction diaries were used to show that the four tiled decks that were suffering latex leaching were all exposed to rain before they were grouted. The six unaffected decks at the complex were grouted before it rained.

The lifting of tiles during investigations almost a year later revealed water still trapped in the ribs of tile adhesive. These decks have an acrylic waterproofing membrane applied over the screed. Often, the residual water had caused the tile adhesive to discolor. This discoloration was present where water had access to the grooves in the adhesive, but was not present where the adhesive rib was closed off. 

Clearly, grouting the tiling helps prevent latex leaching, since even though the grout would allow some moisture to pass, it appears to prevent rainwater from filling the grooves in the tile adhesive. It appears that this liquid water extracts uncured latex or polymer from the day-old adhesive. The movement of moisture under vapor pressure, particularly when sunlight warms the tile surface, takes it to the surface of the grout joints, where, on evaporation, the residues are deposited.

The same applies for wall tiling applications: grouting soon after installation is important in the prevention of water entry. If the wall has an open top, such as a fence or balustrade, it is important to seal the top, possibly with a capping, to prevent water entry.

So, while water entry into ungrouted tiling may not be the only cause of latex leaching, it is certainly a major contributory factor. 

Conclusions

While latex leaching has occasionally been mentioned in professional tile journals for over 30 years, it’s more plentiful today due to changes that have occurred in tiles, tile installation, and construction. These changes include the combination of larger, denser tiles, increased use of latex/polymer-modified mortars and thin-set adhesive, and greater use of membranes and crack-suppression systems under tiles. Under these conditions, the modified cement products take longer to cure, and in some cases, much longer to cure.

If ungrouted tiling is flooded, there is a far greater likelihood of latex leaching occurring, so external tiling should be grouted as soon as possible, to prevent wholesale entry of water into any voids under the tiles. This means covering the ungrouted work if there is any chance of rain. No instances of latex leaching were encountered when rapid-setting adhesive had been used, but the tiling should still be protected if rapid-setting products are used. 

The information supplied by tile adhesive manufacturers is generally remiss when it comes to warning about likely delays to curing and setting times when dense tiles are installed over impervious substrates, and no information was found warning that latex leaching could occur if ungrouted tiling was flooded. More detailed information needs to be inserted into specification and instructions underlining the importance of protecting unfinished tiling from rain and flooding. If the tiling is inundated the wet vacuuming and adequate drying time must be allowed before grouting to avoid latex leaching.

There also appears to be an opportunity for chemical engineers to test if some adhesive additives are greater contributors to latex leaching than others. This could allow for the development of superior external tiling adhesives that would be less likely to present with latex leaching.

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